Swine dysentery is a mucohemorrhagic, diarrheal disease that affects primarily weanling pigs, but may affect larger pigs. The disease is often referred to as bloody scours, bloody dynsentery, hemorrhagic dysentery, mucohemorrhagic diarrhea, or vibrionic dysentery. The disease occurs in many swine-raising areas of the world.
Morbidity is usually greater than 90% in weanling pigs and mortality may reach 75%. Experimentally, swine dysentery may decrease the rate of weight gain two fold and decrease efficiency of feed conversion threefold, as compared with uninfected control pigs. The disease causes tremendous financial losses because of death and decreased rate of growth of infected swine.
The cause of swine dysentery is, as yet, ill defined. In the past, Vibrio coli has been associated with the disease. More recently, a large spirochete Treponema hyodysenteriae, acting in association with other intestinal microorganisms, is thought to be the cause of the disease. At present, the only reliable method of experimental reproduction of the disease is to inoculate susceptible pigs with colonic mucosa and colonic contents of pigs acutely affected with the disease.
The outlook for successful prevention and control of swine dysentery has not been promising because no product previously approved for use in the United States has completely prevented recurrence of the disease. Many swine owners have ultimately had to depopulate, clean, disinfect and restock when the disease became enzootic. It appears that any immunity that develops from natural infection is short lived, and little optimism is expressed concerning the early development of a useful immunologic agent or vaccine.